Bell System Practices Plant Series Adjustments page 3

CONTENTS
Tight-tape Switch Assembly (28B Unit)
Tight-tape arm .
Tight-tape bail yield spring . . . . . .
Tight-tape switch . . . . . . . . . . . . . . .
Tight-tape switch bracket . . . . . . . .
Top Plate Assembly (28B Unit)
Top plate (fixed head) .
INDEX OF FIGURE S
Length of Stop Pulse (Figure 1) . .
Pulse Length Requirements for
Distributor Contacts No. 1
Through No. 5 (Figure 2) . . . . . . . . . . .
Pulse Length Requirements for
Auxiliary Contacts A and B
(Figure 3) . . . . . . . . . . . . . . . . . .
. . . . . . •
Pulse Length Requirements for
Storing Switch Contacts No. 1
Through No. 5 {Figure 4)............
Pulse Length Requirements for
Storing Switch Auxiliary
Contacts {28C Unit) (Figure 5) .
Pulse Length Requirements for
Storing Switch Auxiliary
Contacts {28B Unit) (Figure 6) . . . . . . .
Pulse Length Requirements for
Storing Switch Auxiliary
Contacts {28B Unit Fixed Head)
(Figure 7)
• . . . . . . . .
1. GENERAL
1. 01 This section contains the requirements
and adjusting procedures for the
tenance of the 28B and 28C transmitter -distrib­
utor units. The material herein, together with
the section containing the general requirements
for teletypewriter apparatus,
plete adjusting information for maintenance of
these units.
1. 02 This section is reissued to combine the
requirements and adjustments for the 28C
transmitter-distributor unit with those for the
28B transmitter-distributor unit and to bring up
to date the requirements and adjusting proce­
dures for both of these units.
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main­
provides com­
ISS 3, SECTION 573-127-700
1. 03 In this section, left or right, front or rear,
and up or down refer to the apparatus in
its normal operating position as viewed from
the operator's position in front of the unit.
Parts are shown in an upright position unless
otherwise indicated.
1. 04 The cover may be removed for inspection
of the unit. However, before any mainte­
nance procedures are started, the unit should
first be removed from its subbase to disconnect
the power and to permit the unit to be turned
bottom upward so that parts on the bottom of the
unit are more accessible.
1. 05 Where a requirement calls for the clutch
to be disengaged,
must be fully latched between its triplever and
latchlever so that the clutch shoes release their
tension on the clutch drum. When engaged, the
clutch-shoe lever is unlatched and the clutch
shoes are wedged firmly against the clutch drum.
Note: When rotating either the sensing shaft
or distributor shaft by hand, the clutch does
not fully disengage upon reaching its stop
position. In order to relieve the drag on
the clutch and permit the shaft to rotate
freely, apply pressure on the
clutch disc with a screwdriver to cause it
to engage its latchlever,
gage the internal expansion clutch shoes to
prevent them from dragging on the clutch
drum.
1. 06 The figures in this section show the ad-
justing tolerances,
parts, and spring tensions.
are arranged so that the adjustments are ar­
ranged in the sequence that would be followed if
a complete readjustment of the apparatus were
being made. Where an illustration shows inter­
related parts, the sequence that should be fol­
lowed in checking the requirements and making
the adjustments shown is indicated by the letters
(A), (B), (C), etc.
Note: On all 28C units having 2-cycle cams,
both halves of the cam-sleeve should be
checked.
1. 07 Unless otherwise indicated, the require­
ments and adjustments in this section are
common to both the 28B and 28C transmitter­
distributor units.
the clutch-shoe lever
lug of the
and thus disen­
positions of moving
The illustrations
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